Gas turbine engines typically include a compressor for compressing air. The compressor includes a series of stages of blades rotating around a shaft. The compressed air is mixed with a fuel and channeled to a combustor, where the mixture is ignited within a combustion chamber to generate hot combustion gases. The combustion gases are channeled to a turbine. The turbine section of a gas turbine engine contains a rotor shaft and one or more turbine stages, each having a turbine disk (or rotor) mounted or otherwise carried by the shaft and turbine blades mounted to and radially extending from the periphery of the disk. A turbine assembly typically generates rotating shaft power by expanding hot compressed gas produced by the combustion of a fuel. Gas turbine buckets or blades generally have an airfoil shape designed to convert the thermal and kinetic energy of the flow path gases into mechanical rotation of the rotor.
In a compressor, as well as in a turbine, engine performance and efficiency may be enhanced by reducing the space between the tip of the rotating blades and the respective casing to limit the flow of air over or around the top of the blade that would otherwise bypass the blade. For example, a compressor blade may be configured so that its tip fits close to the compressor casing during engine operation. During engine operation, however, blade tips may rub against the casing, thereby increasing the gap and resulting in a loss of efficiency, or in some cases, damaging or destroying the blade set. Blade material may be transferred to the compressor case creating scabs on the casing that extend into the clearance between the blades and casing, further aggravating any rubbing against the blade tip. In addition, the high speeds that the compressor blades are moving at increase the local temperature at the blade tip such that the metal blade tip may melt. The melting or softening of the blade tip may then lead to additional removal of the blade tip material when rubbed against the compressor case.
Thus, an improved design of a compressor blade and a compressor blade and case assembly is desirable in the art.